The principal objective of this study is to understand the functional pathways underlying the visual processing of motion in the human brain. The subjects for the study will be a group of normal adults and stroke patients with focal lesions in the occipital, temporal or parietal lobes, whose deficits will be also characterized on neurological, neuropsychological, neuro-ophthalmological and neuroanatomical dimensions. Recent physiological and computational advances in the understanding of primate motion analysis provide the framework for the experimental studies proposed in this project. Two classes of problems in visual motion processing will be addressed: (1) detection and measurement; and (2) the use of motion measurements for visual tasks such as the separation of figure from the background or for the derivation of three dimensional structure, for example. The second objective of the study is to learn whether deficits of motion and form processing tend to be associated with functionally and structurally distinct systems in the brain. The third objective is to identify the specific motion deficits that may be correlated with visual-spatial impairments and with poor performance on neuropsychological tasks designed for assessing right hemisphere functions. This might provide the basis for the remediation programs of visuo-spatial deficits. We are specifically interested in the correlations of visual motion deficits and stereopsis, contrast sensitivity, acuity and form.